Composite structures are desirable in many industries for many applications. For example, aircraft, space, and land/sea vehicles employ a variety of composite materials in their fabrication. As in the case with other materials, composite materials sometimes have to be repaired. One of the processes typically involved in repairing composite materials is a curing process. A curing process is normally carried out at an elevated temperature. This elevated temperature curing process creates difficulties in repairing composite materials when the composite material is in the form of a composite structure that is already integrated into an aircraft or other vehicle.
One method of repairing composite structures on, for example, an aircraft is to disassemble the aircraft or a portion thereof so that the composite structure may be repaired and subsequently cured in an oven or autoclave. However, this method is often extremely costly and wastes a considerable amount of time when repairing an aircraft.
Another method of curing composite structures on an aircraft is using one or more heating blankets that lay on top of the area of the composite structure that is being repaired. However, some problems associated with the use of heating blankets are that many heating blankets are only good up to a temperature of approximately 500° F. and the heating blankets have a tendency to adhere to the composite materials that are being cured, which may be detrimental to the repair process.
Another method of curing composite materials on an aircraft is to use portable ovens. However, many prior portable ovens that have been used for on-aircraft repair of composite materials have only been adequate for low temperatures, such as a maximum of 260° F.
Another method of curing composite materials on an aircraft is to use a portable system that includes the following: an open-sided oven having an inner chamber, a first insulation surrounding the inner chamber, an outer chamber surrounding the first insulation, and a second insulation disposed on an outside surface of the outer chamber. A thickness of the first insulation and a thickness of the second insulation are such that a surface temperature of an outside surface of the second insulation is no more than 140 degrees Fahrenheit when the inner chamber is at a temperature of at least 500 degrees Fahrenheit. A hot air distribution manifold is disposed within the inner chamber, a cold air distribution manifold is disposed within the outer chamber, and an exhaust chimney having an insulative material coupled to an outside thereof is coupled to the outer chamber. The hot air distribution manifold comprises a plenum, a plurality of dispersion tubes coupled to the plenum, and a plurality of orifices formed in each dispersion tube.
The system further includes a hot air supply system coupled to the hot air distribution manifold of the oven via a hot air supply tube to supply superheated dry air to the hot air distribution manifold, a cold air supply system coupled to the cold air distribution manifold of the oven to supply cold dry air to the cold air distribution manifold, and a plurality of hot air exhaust passages formed in the inner wall of the oven. The hot air exhaust passages are adapted to transport hot air within the inner chamber to the outer chamber. A ratio of a total area of the hot air exhaust passages to a total area of the orifices of the dispersion tubes is equal to at least one.
The system further includes an insulative seal disposed around a perimeter of the inner wall, a bolt and a nut coupling the inner wall and the outer wall, and a retaining plate extending around an inside of the inner chamber adjacent the perimeter to retain the insulative seal in its place. A plurality of hot air guide plates are coupled to the inner wall and disposed within the outer chamber. Each hot air guide plate has a trough adapted to receive hot air from a respective hot air exhaust passage and transport the hot air within the outer chamber. The system further includes an insulative rope disposed between the inner box and the outer box adjacent the first insulation and extending around a perimeter of the inner wall. A handling structure is also coupled to an exterior of the oven.
This portable system has been experimentally tested on B-2 bombers over the past three years.